It is a known fact for fuel cells, especially high temperature fuel cells (such as SOFC fuel cells), that the cathode-side gaseous reactant (e.g., the reaction air) should be pre-warmed to bring it to the required reaction temperature. This is conventionally performed in a separate high temperature heat exchanger. Such a heat exchanger, however, is bulky, heavy and expensive. Moreover, such a heat exchanger necessitates complex tubing as well as a cost-intensive regulating and control system.
It is an object of the present invention to provide a fuel cell which effects the necessary warming of the cathode-side gaseous reactant without the aforementioned disadvantages.
Accordingly, an end or intermediate plate, which is arranged on or between the various electrolyte/electrode units (individual cell), is designed so that, in terms of flow before an inlet region, particularly a cathode-side inlet region, a heat exchange region is incorporated, in which heat is removed from an anode side and thus the gaseous reactant (e.g., air) is heated to the required reaction temperature.
A core idea of the present invention thus is to integrate a heat exchanger, for example, in a bipolar plate, and to conduct the gaseous reactant that must be heated (e.g., the air) along the hot anode side. The gaseous reactant is not supplied to the appropriate electrode (e.g., cathode) for generating power until it has flowed through this area acting as a heat exchanger.
The end or intermediate plate can be designed so that, for example, a reversal of the flow direction of the gaseous reactant is accomplished. In this way, the gaseous reactant can be conducted through the heat exchanger in a serpentine fashion in order to enable even better heat transfer in the heat exchanger.
The end or intermediate plate (e.g., bipolar plate) preferably contains three flow regions, specifically an anode flow section between the end or intermediate plate and an adjacent anode of an individual cell, a return current heat exchange section adjacent to the anode flow section, and a cathode flow section between the end or intermediate plate and a cathode of another individual cell.
Pursuant to a particularly preferred design, the end or intermediate plate is composed of at least two separate partial elements that can be joined together. At least part of the heat exchange section is included between the two partial elements, and the heat exchange section is connected in terms of flow with the region that later forms the cathode section. If a baffle is arranged between the two partial elements, a serpentine-conducted flow is easy to produce, so that the direction of flow of the gaseous reactants in both partial sections is in the opposite direction.
For a design of the individual flow regions, spacer elements, e.g., in the shape of nubs, can be provided on the individual sides of the end or intermediate plates, as well as between the partial elements, so that the spacer elements rest either against each other or against the individual cells. The nubs can be produced through an embossing or deposition method and shaped as required.
A simple design of the present invention is described in the following in more detail while referencing the attached FIGURE.